The present invention relates to the field of semiconductor manufacturing, and more particularly to a system and method for automatically conducting a leak test for a vacuum system used in the manufacturing of semiconductor devices.
The use of vacuum systems in the manufacture of semiconductor devices is well known in the semiconductor industry. Vacuum systems play a critical role in semiconductor processes such as deposition, etching and ion implantation. The integrity of vacuum systems used in semiconductor processing systems is critical to device yields. For example, in deposition systems, partial pressures of air constituents such as oxygen can reduce the adherence and alter the electrical properties of deposited films. In etching systems, air leaks can affect the basic process chemistry and prematurely erode the photoresist overlay. Deposition and etching systems are typically pumped to some low base pressure prior to introduction of the process gases to minimize the background air contamination. Ion implantation method has been used for placing impurity, or doping, ions in a semiconductor material such as a silicon substrate at precisely controlled depths and at accurately controlled dopant concentrations. Since the wafer surface cannot be contaminated other than by the intended impurity ions, no contamination in the ion implanter components can be tolerated.
Semiconductor devices are typically manufactured by the use of advanced machines for various processes such as deposition, etching and ion implantation. The vacuum systems are often a critical part of these advanced machines. The machines typically go through a manufacturing cycle to produce a batch of the semi-finished or finished semiconductor device. The manufacturing cycle typically includes a plurality of phases such as a set-up phase, a start phase, one or more operational phases, a shutdown phase and an end phase. On completion of the end phase, which indicates a completion of the manufacturing cycle, the semi-finished or finished semiconductor device may be passed on to the next-in-sequence machine for further processing. The machines typically wait in an idle state between the end of one manufacturing cycle and the start of the next manufacturing cycle. The duration of the idle state may vary from a few minutes to several hours depending on the manufacturing volume.
Predictability, reliability, repeatability and cost are critical in an application such as this, where a leak in a vacuum system may result in the stoppage of a production line. The production loss and the subsequent rework may cost millions of dollars in lost profits. The following U.S. patents, which describe various vacuum system leak detection apparatus and methods, are hereby incorporated herein by reference: Chamber Effluent Monitoring System and Semiconductor Processing System Comprising Absorption Spectroscopy Measurement System and Methods of Use (U.S. Pat. No. 6,154,284), and Leakage Detection Apparatus Equipped With Universal Adapter Head and Method of Testing (U.S. Pat. No. 5,777,209).
Conducting leak tests to preserve the integrity of the vacuum systems is highly desirable. Presently, the machines often deploy sophisticated and expensive instruments such as mass spectrometers to monitor the integrity of vacuum systems during the manufacturing cycle. However, many of these instruments are designed to detect particulate matter and often do not conduct leak tests for the vacuum systems during the idle cycle. It would be preferable to automatically conduct the leak tests on a frequent or periodic basis and document the results. It would be desirable to identify a machine equipped with a leaky vacuum system and prevent its further use until the vacuum system has been repaired.
The problems outlined above are addressed by a system and method for automatically conducting a leak test for a vacuum system used in the manufacturing of semiconductor devices, as described herein.
In one embodiment, the method for automatically conducting a leak test for a vacuum system, includes receiving a process status input representing the completion or non-completion of a manufacturing cycle. On determining that the process status is in a completed state, the vacuum system is isolated from the atmosphere by closing the isolation valve. In one embodiment, the first pressure input received represents the initial pressure measured at the beginning of the leak test. At the expiration of a timer, a second pressure input is received and compared to the first pressure input. If the difference between the second pressure and the first pressure is greater than a configurable threshold pressure then the vacuum system is determined to be leaky. In another embodiment, a series of pressure measurements are collected during the leak test duration. If at least one of the pressure measurements included in the series of pressure measurements collected exceeds a threshold pressure value then the vacuum system is determined to be leaky. In response to the determination of the vacuum system leak, an interlock signal to disable the operation of the vacuum system is activated.
The system to implement the method includes a first circuit section, a second circuit section and a third circuit section. The first circuit section is configurable to receive a first signal representing status of the set point for the output power and a second signal representing the output power of the power supply system. The first circuit section is configurable to receive a process status signal and generate a first output signal to close an isolation valve. The second circuit section, which is electrically coupled to the first circuit section, is configurable to activate a timer in response to receiving the first output signal. The third circuit section, which is electrically coupled to the first and second circuit sections, is configurable to receive a pressure input signal representing the pressure inside the main processing chamber. The third circuit section is configurable to compare the pressure input signal to a threshold pressure value and determine the vacuum system is leaky if the value of the pressure input signal is greater than the value of the threshold pressure.
In another embodiment, a processor executes program instructions stored in memory to implement at least some aspects of the system or method. According to this embodiment, the system includes a processing unit, memory coupled to the processing unit and a program included in the memory. The program is executable by the processor to implement conducting a leak test for a vacuum system.